Validations of values using JSON Schema

Helm 3 introduced support for validation of values using schema files which follow JSON Schema. Helm charts in this repository also makes use of this feature by defining values.schema.json file for each sub-chart.

Guidelines for developers regarding usage of schema files:

  • If you are adding a new entry to or modifying an existing entry in the values.yaml file of a subchart, you must update the respective values.schema.json file to match this change.
  • The first iteration of this task is expected to be completed when all the sub-charts are equipped with a schema file. You can check the progress of the first iteration in the related epic. Future iterations will focus on improving and polishing these schema files and enhance their efficiency and usability.
  • All settings configurable via values.yaml must have type validations (ensure they accept only the correct data types as values) implemented in the values.schema.json file. This must be completed in the first iteration.
  • During the first iteration, validation of required fields can be limited to ensuring the settings a user has defined in their values.yaml file is sufficient to spin up a pod with just that component, and without any error being reported in the logs. In future iterations, this should be expanded to ensure the pod is, in fact, functional. This involves deeper testing.

Validating immutable fields

Some fields in the Kubernetes spec are immutable. Ensure that no changes to immutable fields would impact customer upgrades.


A Statefulset contains a set of immutable fields. Ensure that none of the fields that are not allowed to be modified are indeed not modified. This negatively impacts the ability to perform upgrades. Example error message:

Error: UPGRADE FAILED: cannot patch "a-gitaly" with kind StatefulSet
  StatefulSet.apps "a-gitaly" is invalid
  spec: Forbidden:
    updates to statefulset spec for fields other than
    'replicas', 'template', and 'updateStrategy'
    are forbidden